WO 2010/114359 describes a motion compensation device of the same applicant as the present application. In WO 2010/114359 the carrier frame is compensated for x-axis rotational movement, y-axis rotational movement as well as z-axis translational movement due to water motion. Taking into account that the crane is carried on the carrier frame, this also compensates the crane. According to WO 2010/114359 there is an actuator system comprising at least three cylinder-piston-units, which are arranged essentially parallel, especially essentially vertical. In use these cylinder-piston units can be extended or shortened simultaneously to adjust the vertical height—in z-axis direction—of the carrier frame with respect to the vessel. During use, when a vessel is essentially stationary on its place this is the dominant vessel movement to be compensated for when the vessel goes up and down with the—often relatively slow and long—wave movement of the water. The less dominant sideways roll of the vessel and aft-front pitch of the vessel are compensated for by adjusting the same cylinder-piston-units differently with respect to each other. WO 2010/114359 describes a constraining system restricting x-axis translational movement, y-axis translational movement and z-axis rotational movement of the carrier frame with respect to the base to movements necessary to allow for z-axis translational movement, x-axis rotational movement and y-axis rotational movement of the carrier frame with respect to the base by said actuator system. The concept behind WO 2010/114359 is that in most cases, it suffices to compensate only for z-axis translational movement, x-axis rotational movement and y-axis rotational movement of the vessel. The other three degrees of freedom of movement of the vessel (i.e. the z-axis rotational movement, the x-axis translational movement and the y-axis translational movement) need not be compensated for because they are under many circumstances negligible. These other three degrees of freedom of movements being negligible can have different reasons. When, for example, the vessel is anchored and/or kept in position by a dynamic positioning control, these other degrees of freedom of movement are already being taken care of. Although the present invention is not limited to this concept of WO 2010/114359, the present invention might be applied with this same concept.
In WO 2010/114359 the compensation aims at maintaining the carrier frame in a non-changing position with respect to the fixed world. This is very helpful when a crane, provided on a vessel moving due to local water motion, is used to deliver a load onto a construction on shore or fixed in the sea bed or to pick up a load from such a construction. However, when using such a motion compensation device for compensating a crane which is picking up a load from the vessel on which the crane itself is supported, the crane and vessel will move with respect to each other as the carrier frame supporting the crane is maintained motionless with respect to the fixed world whilst the vessel is moving with respect to the fixed world. Consequently picking up a load from the deck of the vessel and placing a load on the deck of the vessel is impeded by relative motion, causing dynamic and snatch loads creating unsafe situations.